1. Field of the Invention
The present invention relates to an intake device for outboard motors, and more particularly to an intake device for outboard motors equipped with a V-type engine for vertical installation.
2. Description of the Related Art
Conventionally, a general type of intake device for outboard motors equipped with a V-type engine has surge tanks provided for respective cylinder banks (see e.g. Japanese Laid-Open Patent Publications (Kokai) No. H09-42088 and No. 2002-242777). However, the conventional intake device, which is provided with two surge tanks, needs a complicated construction, which inevitably increases the size of the device. Further, it is required to form a bend in an intermediate portion of an intake passage member connecting between each surge tank and an associated cylinder head, and the bend causes intake air resistance, which leads to degradation of the intake performance of the outboard motor.
On the other hand, conventionally, there has also been an intake device for outboard motors equipped with a V-type engine, which is provided with a single surge tank (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2004-232591). This intake device has funnel-shaped members provided in the surge tank, as inlet ports each connected to an intake passage member. The funnel-shaped members are arranged in a manner isolated from each other so as to avoid interference between adjacent ones thereof, whereby the improvement of intake efficiency is achieved.
However, an intake device for outboard motors, provided with the throttle valve disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2004-232591 suffers from a problem that it is difficult to secure a sufficient capacity of a surge tank due to the construction of an outboard motor, and hence, when a sufficient capacity of a surge tank cannot be secured, it is impossible to provide the funnel-shaped members.
Further, conventionally, another intake device for outboard motors equipped with a V-type engine has been disclosed in which a single mechanical throttle body is provided in a central part of a V-bank (see e.g. Japanese Laid-Open Patent Publications (Kokai) No. 2001-336425 and No. 2002-242682). The mechanical throttle body requires provision of a lever and a linkage for opening and closing a throttle valve, and hence it is required to dispose the mechanical throttle body such that the lever and the linkage do not cause interference with components parts therearound. For this reason, in the conventional intake device of an outboard motor equipped with a V-type engine, the throttle body is disposed above the surge tank and the manifold of the engine at a location slightly away therefrom, with intake passage members thereof oriented in the longitudinal direction of the outboard motor, which causes an increase in the vertical dimension of the conventional intake device.
Insofar as a throttle valve is concerned, there has conventionally been disclosed an electronically-controlled throttle body (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2004-270563). The electronically-controlled throttle body can have a smaller size than the mechanical throttle body.
In the above-described conventional intake devices for outboard motors equipped with a V-type engine, it is easy to simply replace the mechanical throttle body with the electronically-controlled throttle body. However, the problem concerning the size of the intake device cannot be solved by simply changing the mechanical throttle body to the electronically-controlled throttle body.
In addition, the conventional intake devices have a silencer mounted to the end of an intake port of the throttle body in a protruding manner, which causes further increase in the size of the intake device.
As described above, the conventional intake devices for outboard motors cannot avoid increase in device size or degradation of intake performance.